
Si3216
26 Rev. 1.0
Not Recommended
f
o
r N
e
w
D
e
si
g
n
s
The subcircuit above can be substituted into any of the ProSLIC solutions as an optional bias circuit for Q5, Q6. For
this optional subcircuit, C7 and C8 are different in voltage and capacitance to the standard circuit. R23 and R24 are
additional components.
Table 17. Si321x Optional Bias Component Values
Component Value Supplier/Part Number
C7,C8 100 nF, 100 V, X7R, 20% Murata, Johanson, Venkel
R23,R24 3.0 k
, 1/10 W, 5%
Table 18. Component Value Selection for Si321x/Si321xM
Component Value Comments
R28 1/10 W, 1% resistor
For V
DD
= 3.3 V: 26.1 k
For V
DD
= 5.0 V: 37.4 k
R28 = (V
DD
+ V
BE
)/148 µA
where V
BE
is the nominal VBE for Q9
R29 1/10 W, 1% resistor
For V
CLAMP
= 80 V: 541 k
For V
CLAMP
= 85 V: 574 k
For V
CLAMP
= 100 V: 676 k
R29 = V
CLAMP
/148 µA
where V
CLAMP
is the clamping voltage for V
BAT
Table 19. Component Value Selection Examples for Si321xM MOSFET/Transformer DC-DC Converter
VDC Ringing Load/Loop Resistance Transformer Ratio R18 R19, R20
3.3 V 3 REN/117 1:2 0.06 7.15 k
5.0 V 5 REN/117 1:2 0.10 16.5 k
12 V 5 REN/117 1:3 0.68 56.2 k
24 V 5 REN/117 1:4 2.20 121 k
Note: There are other system and software conditions that influence component value selection; so, please refer to “AN45:
Design Guide for the Si3210 DC-DC Converter” for detailed guidance.
Table 20. Component Value Selection Examples for Si321x BJT/Inductor DC-DC Converter
VDC Ringing Load/Loop Length L1 R17 R18 R19, R20
5 V 3 REN/117 33 µH 100 0.12 16.5 k
12 V 5 REN/117 150 µH 162 0.56 56.2k
24 V 5 REN/117 560 µH 274 2.2 121 k
Note: There are other system and software conditions that influence component value selection, so please refer to “AN45:
Design Guide for the Si3210 DC-DC Converter” for detailed guidance.
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